A number of techniques for controlling errors in communication transmissions exist. One such technique is an automatic-repeat-request (ARQ) scheme. A code with good error-detecting capability is used in an ARQ scheme. The receiver attempts to detect errors according to its error-detection mechanism. Data is segmented into numbered packets. If no errors are detected in a packet of data, the receiver assumes that the packet is error-free, and the receiver accepts the packet, and via a return channel, informs the transmitter that the packet was successfully received and identifies the packet by number. If errors are detected in the packet of data, the receiver, via the return channel, informs the transmitter and requests retransmission of the packet by number. This process of transmission, informing, and retransmission continues until an entire message is successfully received.
Occasionally, a communication system fails, and it becomes necessary to repair or test it. A common, if not indispensable, tool used to test and/or debug a communication system is a loopback, which isolates portions of the communication system from the remainder of the system. The remaining part of the system is tested through the loopback path, by sending known test patterns through the path, and checking to be sure that the data matches the pattern at each part of the path. When a path tests out successfully, the fault is determined to exist in the isolated portion of the system.
An ARQ system breaks down and fails to function properly if the return channel is disturbed or cut-off, because the transmitter and receiver must maintain constant communication to insure that all message packets are received to the satisfaction of the receiver. Without this duplex system, no data is successfully transferred. Thus, an ARQ system cannot operate in a simplex or one way only mode. Consequently, if a fault occurs in a system with an ARQ protocol, it is impossible to test the data by sending a test pattern, as such a pattern will cause the ARQ protocol to break down and no information will be successfully transferred. Testing is effectively impossible.
An ARQ system breaks down and fails to function properly if the return channel is disturbed or cut-off, because the transmitter and receiver must maintain constant communication to insure that all message packets are received to the satisfaction of the receiver. Without this duplex system, no data is successfully transferred. Thus, an ARQ system cannot operate in a simplex or one way only mode. Consequently, if a fault occurs in a system with an ARQ protocol, it is impossible to test the data by sending a test pattern, looping it back in the system, and returning the data back to the same entity. Such a pattern will cause the ARQ protocol to break down and no information will be successfully transferred. Testing in this manner is effectively impossible.
Accordingly, there is a need for a method of testing a system that utilizes an ARQ protocol.